This invention relates to fittings for connecting electrical cables and flexible conduit to a panel and specifically to an improved fitting that allows easier insertion of the cable or conduit into the trailing end of the fitting.
Historically, armored cable (AC) or metal-clad cable (MC) has been connected to a panel by a tubular fitting including a leading end having a threaded nose and a trailing end having a lateral screw mounted laterally through the fitting wall. The threaded nose was inserted into an aperture in the panel and a locknut tightened thereon to secure the fitting to the panel. AC or MC cable was then inserted into the trailing end and the lateral screw tightened to secure the cable to the fitting. Since the fitting, the panel, the locknut, the lateral screw, and the jacket of the cable were typically constructed of metal, securing the cable to the panel in the aforementioned manner would create good electrical continuity or ground between the cable and the panel.
To reduce the time and effort required to connect AC or MC cables to panels, the present inventor has introduced several snap-engagement type fittings. Early examples of a snap-in connector were disclosed in U.S. Pat. No. 6,043,432, filed Jan. 15, 1998 and U.S. Pat. No. 6,080,933, filed Oct. 2, 1998 and both incorporated herein by reference in their entirety. These patents disclosed a snap fitting that included a spring steel locking ring to receive an armored cable and lock it into the trailing end of the connector. The spring steel locking ring included outward directed tangs allowing unidirectional insertion into the connector and inward directed tangs to permit reception of the armored cable into the trailing end and restrict its withdrawal from the connector.
U.S. Pat. No. 6,335,488 filed Jun. 26, 2000 and incorporated herein by reference in its entirety, improved upon the snap engagement fitting by increasing the number of inward directed tangs from two to three and varying the spacing of the inward directed tangs to increase cable engagement and thus better prevent its removal by a rearward withdrawal motion.
A further improvement to the snap engagement fitting was disclosed in U.S. patent application Ser. No. 09/792,184 entitled xe2x80x9cElectrical Connectorxe2x80x9d, filed Feb. 23, 2001 and incorporated herein by reference in its entirety. Ser. No. 09/792,184 provided a snap engagement fitting with an additional aperture in the cylindrical housing in the trailing end for facilitating removal of the trailing end snap-in spring steel retainer. It also included an alternative internal flange system on the trailing end for improving the retention of the spring steel adapter.
U.S. patent application Ser. No. 10/053,076, filed Jan. 17, 2002 and incorporated herein by reference in its entirety, further improved the snap engagement fitting by improving the continuity between the fitting, the cable, and the junction box. The disclosure provided a snap ring in the trailing end that included at least one grounding tang cantilevered from its outer circumference. The grounding tangs, located near the trailing end of the spring member, extend at a rising slope from their supported end to a crest and then at a downward slope to its trailing end. When pressed into a hole in a junction box, the grounding tangs are compressed toward the fitting until the crest clears the hole whereupon the springiness of the grounding tangs and the downward slope cause the fitting to be drawn tightly against the junction box wall, thereby improving continuity of the fitting.
U.S. patent application Ser. No. 10/256,641, filed Sep. 27, 2002 and incorporated herein by reference in its entirety, further increased the continuity of the snap engagement fitting by providing locking tangs integral with the grounding tangs thereby making a greater portion of the periphery of the snap ring is available for forming the grounding tang. The grounding tangs could therefore be made larger and thereby improving continuity and lowering the millivolt drop between the grounding tangs and the junction box. Electrical continuity was further enhanced by the design of the grounding tangs, which extend from the snap ring at a rising slope to a crest and then at a downward slope to their free ends thereby enabling the downward slope portion of the grounding tangs to pull against the surrounding walls of the junction box and draw the fitting tight against the side of the box.
U.S. patent application Ser. No. 10/286,228, filed Nov. 1, 2002 and incorporated herein by reference in its entirety, provided a snap-in engagement fitting for securing electrical metallic tubing (EMT) to a panel. The fitting provided a split ring on its trailing end that included a plurality of locking tangs lanced longitudinally and bent inwardly to a smaller diameter than the outer diameter of EMT that it was used in conjunction with. Arcuate edges were provided on the leading ends of the locking tangs to dig into the outer surface of the EMT and thereby secured it to the trailing end of connector. The large contact area between the locking tangs and the EMT improved continuity and lowered the millivolt drop.
Although several improvements have been made to the original design of the snap engagement electrical fitting, as a result of the limited space available for flexing of the locking tangs, the fitting has at times proved less than ideal for engaging oversized AC or MC cable. Typically the tubular connector of the snap engagement fitting is secured to a panel in close proximity to adjacent connectors. The outer dimension of the connector must therefore be limited in size. As a result of limiting the size of the connector, past snap engagement fittings for AC or MC cable have limited the outward travel of the cable locking tangs and made it difficult to insert oversized cable. What is needed therefore is a snap engagement fitting that allows unimpeded outward flexing of the cable locking tangs while also allowing mounting of several fittings in a panel in close proximity to one another.
The purpose of the present invention is the improvement of the fitting for snap engagement of armored cable to a panel. Specifically, the fitting has been modified to allow unimpeded outward flexing of the cable locking tangs while at the same time allowing insertion of multiple fittings into a panel in close proximity to one another.
These and other advantages will become apparent by reading the attached specification and claims in conjunction with reference to the attached drawings.
The present invention comprises a fitting that provides a trailing end designed for easy snap-in engagement of armored cable of the type that includes a convoluted surface having trough areas and crown areas. The fitting comprises a hollow, tubular, electrically conductive electrical connector having a leading for connecting to a panel and a trailing end for accepting armored cable. A fastening arrangement is provided on the leading end to allow snap-in engagement to a panel. A resilient, electrically conductive, generally cylindrical-shaped split snap ring is secured within the trailing end of the connector. The split snap ring may be described as having a longitudinal axis there through the axial center of the ring. A plurality of locking tangs are lanced longitudinally and bent inwardly to a smaller diameter than the outer diameter of armored cable that the fitting will be used in conjunction with. Edges of the locking tangs are staggered longitudinally within the tubular connector to enable each tang to engage a trough in the surface of the armored cable and thereby hold it fast to the trailing end of connector. The fastening arrangement on the leading end of the fitting is typically a split ring affixed to the nose of the connector. The connector, split ring affixed to the nose of the connector, and the split ring secured within the trailing end of the connector comprise the fitting of the present invention that provides snap-in engagement on both ends of the fitting. The fitting allows the leading end of the connector to be snapped into a standard sized aperture in a panel and also allows armored cable to be snapped into its trailing end. The tight engagement of the locking tangs to the trough areas of the cable provide good surface contact between the locking tangs and the cable, thereby improving continuity and lowering the millivolt drop between the cable, the fitting, and the panel.